Spin-Dependent Transport and Densities of States in Non-collinear Magnetic Barriers

The spin-dependent transport properties in the non-collinear pattern of series of δ-magnetic barriers are studied by using scattering theory and Green＇s function methods. The Green＇s function is obtained by using distorted wave approach and the scattering matrix is related by Fisher-Lee relationship. In addition to reproducing the results of Papp＇s and Xu＇s in parallel and antiparallel configurations, we also obtain further results, where arbitrary orientations of the magnetic barriers and arbitrary number of barriers are included. The main finding of our results is that the signs of polarizations can be switched around some ＂geometric unpolarized windows＂. The well-known antiparallel configuration has no such characteristics. Furthermore, we discuss spin-related partial densities of states in both polarized and unpolarized structures.     

含磁单极电动力学的电磁对偶对称性自发破缺问题

首先提出了一种认为磁单极的存在将导致电动力学电磁对偶对称性自发破缺的新观点,指出了和这种对称性自发破缺相关联的零质量标量粒子即Goldstone玻子存在的可能性.然后通过对含磁单极电动力学作用量描述困难的分析,提醒读者磁单极的存在给电动力学带来的复杂性和不对称.最后为非高能物理背景的读者提供了两类磁单极即经典场扩展位形类磁单极和点粒子磁单极的概念.     

Influence of Rashba SOI and Polaronic Effects on the Ground-State Energy of Electrons in Semiconductor Quantum Rings

The influence of Rashba spin-orbit interaction （SOI） and polaronic effect on the ground-state energy of electrons in semiconductor quantum rings （QRs） are studied by means of the Lee-Low-Pines variational method. Numerical calculations for GaAs QRs are performed and the results show that the ground-state energy of electrons splits into two branches as E（↑） and E（↓） under the Rashba SOI, which correspond to the spin-up state and spin-down state, respectively. The contribution of the Rashba SOI effect to the ground-state energy of electrons is related to the spin state of electrons and is closely linked to the inner and outer radii of a QR. However, it is independent of the height of the QR. The ground-state energy of electrons decreases due to the polaronic effect in QRs. The energy shift ＆#8710;Ee-LO of the ground-state of the electron induced by the polaronic effect decreases monotonically with increase of the height of a QR and fluctuates with the changes of the radii of QRs. The amplitude of the fluctuation is very sensitive and remarkable to the changes of the inner radius R1 and the outer radius R2.     

ν↓型三能级原子系统中Raman跃迁增强的Kerr非线性效应

在理论上研究了ν↓型三能级原子系统Raman跃迁中的线性和非线性极化率．研究表明：Raman跃迁中，如果原子完全被抽运到与控制光作用的基态时，将导致介质对探针光的线性极化率为零，而三阶非线性极化率不为零．通过减小原子两基态间的无辐射衰减速率γ12，可以极大地增强交叉Kerr非线性效应．     

Effect of Temperature on Polaron Stability in a One-Dimensional Organic Lattice

Effect of temperature on the polaron stability in a one-dimensional organic lattice is investigated within the Su-Schrieffer-Heeger model. The temperature effect is simulated by introducing random forces to the equation of the lattice motion. It is found that the localized polaron state becomes delocalized even at low temperatures. The time of polaron keeping localized depends on the magnitude of temperatures. By taking into account the thermal effect, we find that the dissociation field is weaker as compared with earlier works.     

链间耦合对聚合物中双激子态反向极化的影响

从紧束缚模型出发，研究了链间相互作用对双激子态反向极化的影响.结果发现：加链间耦合后，双激子态仍主要局域在一条链中.当简并破缺较小时，反向极化程度随耦合强度的增加大幅提高；当简并破缺较大时，反向极化程度随耦合强度的增加基本不变. 关键词： 反向极化 双激子态 链间耦合     

激光感生色散光学滤波理论

利用半经典理论，建立了激光感生色散光学滤波的理论模型.通过求解密度矩阵方程，得到 感生极化率.并利用该理论计算出钾694 nm激光感生色散光学滤波器的透射谱，与发表的实 验结果基本符合. 关键词： 激光感生色散光学滤波 透射谱 极化率     

自发产生相干对Y型四能级原子系统探测吸收的影响

在与三个场相互作用的Y型四能级原子系统中,利用密度矩阵方程计算了介质对探测场的吸收,分析了自发产生相干对探测吸收的影响.结果发现:随着自发产生相干的影响,在共振中心处,探测吸收表现出不同的现象.当自发产生相干对探测吸收产生相消干涉时,随着自发产生相干的增强,在共振中心处削弱吸收,出现增益.当自发产生相干对探测吸收产生相长干涉时,随着自发产生相干的增强,在共振中心处出现吸收增强,也即出现电磁诱导吸收(electromagnetically induced absorption,简称EIA),在共振两侧的双电磁感应透明强度(electromagnetically induced transparency,简称EIT)增强,窗口变宽.同时,在能级| 3〉→| 2〉与| 4〉→| 2〉的自发衰减速率比值不变下,当能级|3〉→|2〉与|4〉→|2〉的自发衰减速率减小时,在共振中心处,吸收线宽变窄,共振两侧的透明窗口变宽.     

自旋阀与多层膜巨磁电阻的特性测量及比较

介绍磁性多层膜中自旋极化输运和巨磁电阻效应,简述自旋阀巨磁电阻与多层膜巨磁电阻在材料组成结构和工作原理方面的区别,利用和改造现有的高校物理实验室中的实验仪器并设计简易的实验电路测量这两种类型的巨磁电阻的磁敏特性,并根据实验测量的结果将这两种传感器在其灵敏度和测量范围上进行比较和研究.     

光纤热极化过程的实时测试研究

通过热极化可以使中心对称的熔石英光纤中产生二阶非线性效应和线性电光效应。为了解各热极化过程参量对热极化产生的线性电光效应的影响,利用全保偏光纤马赫一曾德尔干涉仪构造了一套光纤热极化的实时线性电光效应测试系统,并利用其进行了光纤热极化全过程的监控测试。在线测试了热极化过程的一些参量,例如极化电压、极化时间、以及极化温度等对热极化光纤中产生的线性电光效应的影响。实时测试研究表明,在光纤中施加尽可能高的极化电场将可能在光纤中产生较高的线性电光效应。对侧边抛磨光纤结构的热极化器件,考虑到器件的抗强电场击穿能力,可选用3．o～4．0kV左右的极化直流电压。当施加3．0kV左右的极化电压时,热极化优化时间约为16min,最佳热极化加热温度约为190℃。